I'm not sure, but I think this has been covered before, although it's probably been awhile.
No disrespect to Striker[:D] or any of the other Canadains here, but is Canada copying us?
[img]http://www.diemaco.com/images/sal-c8.gif[/img]
[url]www.diemaco.com/sal-carbine%20C8.htm[/url]

There's a really good chapter on the history of the adoption and development of the C7 and C8 rifles in the book "The Black Rifle."
I'm rather fond of the C7 and C8 series myself, as I have always liked the "set it and forget it" A1 upper mated with the A2 brass deflection pylon.
[heavy]

Here are newer variants of the C8, the C8 FTHB and the C8 SFW . I guess it is one of these two that is most likely the variant used by the British SAS, since they procuired a shipment of Diemaco carbines recently.
C8 FTHB
[img]http://www.diemaco.com/images/sal-c8fthb.gif[/img]
C8 SFW
[img]http://www.diemaco.com/images/sal-sfw.gif[/img]